(1) Field of the Invention
This invention relates to screw guns. Screw guns have been developed for use in modern manufacturing (CHEN, U.S. Pat. No. 5,138,913) and construction of structures (NASIATKA, U.S. Pat. No. 3,910,324 and CAST, U.S. Pat. No. 4,625,597). Basically a screw gun is adapted to hold a magazine of screws and automatically advance them to a driving position where they may be driven into the work by a power driven bit. Although this invention is adapted for use with self-tapping metal screws in manufacturing or wood screws in construction of wooden structures such as furniture or cabinets, it is particularly adapted for attaching gypsum wall boards for structures such as habitations or offices. The studs to which the wall board is attached may be either metal or wood.
A construction worker skilled in attaching wall board is one having ordinary skill in the art.
(2) Description of the Related Art
In addition to the three patents referenced above, applicant was aware of the following U. S. patents.
______________________________________ MIZUNO et al 4,404,877 TAKAGI 5,083,483 FARIAN et al 5,109,738 HALSTEAD 3,554,246 DAMRATOWSKI 3,971,421 ______________________________________
All of these devices are characterized by having a small surface on the screw gun which contacts the work piece. In addition, most of the patents referenced above have the electric or air-driven motor integral with the gun.
Despite the developments as shown in the above identified patents, in common practice today, wall board is attached to studs by the workman holding the wall board against the stud with his shoulder or arm, holding a single screw between his fingers and driving the screw with an electric powered drill which has a screwdriver bit thereon. As an alternate to this, at times wood screws are held by a finger and driven by hammer partially into the wood and thereafter driven by a screwdriver.